Struggling with Selective Mutism and Autism

I'm so frustrated with myself. I don't know how I'm supposed to function. I've been having a pain flare, I'm having a rapid cycling episode. I forgot I had an appointment that I've been really looking forward to, and that's what broke me. I have so much shame when I can't talk. What is it called? selective mutism? going nonverbal? I have gotten so overwhelmed an frustrated that I can't talk right now. I've told my mom before that it's an autistic trait but I still don't think she gets it. I don't know what to tell her at this point. I don't want to make her upset. I know its a completely normal experience for autistic people. I still feel so silly/ childish. I'm so frustrated with myself and I feel like it just pushes me further in. How do y'all deal with this??